A recently developed type of electro-optic display is an electrowetting display, as described amongst others in international patent applications WO 2003/071346 and WO 2005/098797.
A disadvantage of the known electrowetting display is the relatively high driving voltages which are required to drive the electrowetting elements of the display. The voltage across the electrowetting elements Vew is in the region of 30V, which if using a conventional battery, at say 3V, requires boosting using a DC-DC booster. A disadvantage of the switching scheme shown is that the power requirements of the DC-DC booster circuit are relatively high. Given the use of such displays in portable electronic devices such as clocks, cellular telephones, etc, power saving is an important desideratum.
U.S. Pat. No. 6,879,135 describes a DC-DC booster circuit. The DC-DC booster circuit includes a number of voltage multiplying stages which have the same circuit structure, and which are controlled in a switched manner using a high frequency clock frequency, at a predetermined switching frequency.
United States Patent Publication US 2005/0195182 describes a driver circuit for driving scan lines of an LCD active matrix panel. The document describes varying a switching frequency of a DC-DC booster circuit. The boost operation clock signal is synchronised with a predetermined edge of a frame synchronisation signal.
It would be desirable to provide an improved way of driving an electrowetting display apparatus.